1. Field of the Invention
The present invention relates to a settlement judgment method for judging whether an object is settled at a target position, or is following up in a positioning control device for moving the object to the target position by an actuator, and to the positioning control device and the disk apparatus, and more particularly to a settling judgment method for a positioning control device for decreasing the settling judgment time and accurately judging the settling, and to the positioning control device and the disk apparatus.
2. Description of the Related Art
A positioning control device for moving an object to a target position is widely used. For this positioning control device, high precision positioning is demanded when used for a disk device, for example. Particularly in a magnetic disk device or an optical disk device, accurately positioning a head to a target track is extremely important to improve recording density. Settling judgment is a method for judging whether the positioning control to this target position is being performed accurately.
In the settling judgment of a positioning control device, it is required to satisfy the predetermined positioning conditions during a predetermined time after moving or after the position deviates. For example, in the case of a magnetic disk device, settling judgment is performed after seek control and during follow up control. In this settling judgment, the completion of settling is judged when the value of the judgment formula based on the positional error continuously satisfies a predetermined slice range for more than a predetermined number of times (number of samples).
As the method for judging settling, a method of predicting the position of the next sample (for example, Japanese Patent Application Laid-Open No. H08-106742), and a method of using an estimated position using an observer (for example, Japanese Patent Application Laid-Open No. H04-298868) have been proposed.
With such prior art, the conditions of settling judgment, particularly the value of slice and the number of samples, are determined based on experience. For example, in order to accurately judge settling, it is preferable to set the value of slice high and also the number of samples high.
In the disk device, for example, the width of the data track is predetermined and the data tracks are arranged next to each other in the radius direction. Therefore if the head moves to an adjacent track after seeking or after settlement judgment during follow up, the data may be erased by error. Or a part of the data may be erased and the S/N of the recorded data drops.
In order to improve the response performance in the seek control of the disk device or recovery control during follow up control, the settling judgment time should be decreased. But if this judgment time is too short, residual vibration after seeking may not be detected, and positioning accuracy may drop after settling completes.
Because of the recent demand for large capacities and higher speeds in disk devices, settling judgment conditions are critical for safety and for the high-speed processing of data, but with the prior art, implementing both a short settling judgment time and good positioning accuracy is difficult.